1. Field of the Invention
This invention pertains to the field of roofing shingles.
2. Description of the Prior Art
Roofing shingles have been made in a continuous process in which the apparatus unrolled a felted sheet and immersed the sheet into a bath of bituminous material to saturate the sheet. The saturated sheet then was coated with a bituminous coating adhesive spread over its top and bottom surfaces. Slate roofing granules were applied to its top surface and a fine powder or sand was applied to the bottom surface. The shingle was then cut into a conventional size of 12 inches by 36 inches for packaging.
A more recent development which is thought to enhance the appearance of the finished shingle roof comprises a two-layer shingle in which a narrow strip of asphalt saturated felt is adhered along the exposed edge of the shingle to give the roof an improved appearance by presenting to the viewer's eye a thicker edge for the shingle. However, the laminating was accomplished by cutting shingles of two different widths at different times on the roofing machine and then in a hand operation laminating the narrower strip to the underside of the wider or conventional size shingle. The extra operation has proved to be cumbersome and the additional conveying and handling apparatus costly and space consuming. The extra laminating operation also presented problems in exactly aligning the two exposed edges of the laminates and achieving good adhesion.
Current technology comprises a roofing shingle which has a broad central area and a narrow strip adhered thereto along one edge of the central area. This roofing shingle has cut-out areas along the edge of the central strip and in the adhered narrow strip. The process for making this improved shingle is described and claimed in U.S. Pat. No. 3,998,685, entitled: APPARATUS AND PROCESS FOR MAKING AN OFFSET LAMINATED ROOFING SHINGLE AND ROOFING SHINGLE MADE THEREBY and assigned to The Celotex Corporation.
Recently, the organic felted material of which the roofing shingle used to be made has been changed to a glass fiber mat which is fire retardant. It is no longer necessary to saturate the glass mat in a bath of asphalt or bitumen. The glass mat is merely coated with an asphalt layer which also easily penetrates into the mat itself.
A newer development is a shingle which has a broad central area and a narrow strip adhered along one edge of the central area. The combination shingle has tabs between cut out areas along the edge which has the double layer of a wide central area and narrow strip as described in the cited patent. A third layer which is a narrow strip of the same material is adhered to the tabs to form a layer underlying and bridging the gaps which separate the tabs.